The present invention relates to the measuring of operating parameters in machines. More specifically, the present invention relates to measuring fluid pressure using a combination of measured and estimated values. Present measurement techniques suffer from cost problems and/or a misplacement of sensor resolution (that is, a low resolution within an area of interest, or a high resolution in ranges outside the area of interest). In some of these systems, such inefficient approaches add significant cost to the system design but realize very little benefit for the machine operator.
In one such example, a vehicle presented its operator with a display of the oil pressure in the engine, either in the form of a simple binary indicator light or small analog gauge. In this prior art system, the oil pressure was measured with sensors having good range and resolution, but the data produced by those sensors was used only to drive very basic output devices. Much of the information in the sensor""s output signal was, therefore, discarded with little or no benefit to the design and operation thereof. That is, even though the system used sensors with good resolution over their whole operating range, that resolution was important only in a small portion of that range and wasted in the remainder of the range.
There is thus a need for further contributions and improvements to engine fluid measurement technology. The present invention satisfies this need in a novel and nonobvious manner.
One object of the present invention to provide an improved fluid characteristic measurement technique, system, and method.
This object and others are achieved by various forms of the present invention. One aspect of the present invention is a method for use in an engine having a first fluid, the operation of the engine being characterized by one or more operating parameters, comprising sensing whether the first fluid pressure is greater than or less than a threshold pressure. If the first fluid pressure is sensed to be greater than the threshold pressure, one or more engine operating parameters are used to estimate the first fluid pressure, and the estimated oil pressure is output. If, on the other hand, the first fluid pressure is sensed to be less than the threshold pressure, a detected pressure of the first fluid is output. In one embodiment of this aspect, the engine operating parameter(s) comprise the engine revolution rate and a temperature of a second engine fluid (such as a lubricant or coolant). In other embodiments, the first fluid is oil.
In another aspect of the present invention, an apparatus comprises a pressure switch with a first output signal that indicates a pressure below a threshold pressure and a second output signal that indicates a pressure above the threshold pressure. An oil pressure sensor outputs a sensed pressure output signal, and an oil pressure estimator outputs an estimate signal. A multiplexer is configured to receive these signals and (1) output the sensed pressure output signal in response to the first output signal, and (2) output the estimate signal in response to the second output signal.
In yet another aspect of the present invention, a system comprises one or more oil pressure sensors that produce a sensed pressure signal that reflects a detected oil pressure; an estimating means for producing an estimated pressure signal; and a selection means in communication with the sensors and the estimating means, wherein the selection means outputs an output signal (1) based on the sensed pressure signal when the detected oil pressure is less than a predetermined threshold, and (2) based on the estimated pressure signal when the detected oil pressure is greater than the predetermined threshold. In some embodiments of this aspect of the invention, the selection means is an analog multiplexor, while in other embodiments, the selection means is a digital multiplexor. In still further embodiments, a controller executes software to control the engine, and the selection means is a conditional operation in the software.